Questions and Answers
What is the primary reason animals typically breed in the spring?
Which factor is primarily responsible for the onset of cyclic reproductive activity in female animals?
What term describes the periods of sexual receptivity in female domestic animals?
How does domestication affect the breeding season of animals?
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What physiological change occurs in females upon reaching puberty?
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Which species are classified as seasonal polycyclic animals?
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What is a unique characteristic of the cyclic reproductive activity in non-seasonal polycyclic animals?
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Which of the following statements is true regarding the physiological state of female domestic animals from puberty onward?
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What is the average duration of oestrus in mature British breed ewes?
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How long does the oestrous cycle last on average?
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What primary role do estrogens play in the oestrous cycle?
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What behavior is commonly observed in ewes during oestrus?
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What hormonal peak occurs around day 6 of the oestrous cycle in cows?
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What is a sign that indicates a ewe is in full heat?
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What effect does low progesterone levels have toward the end of the oestrous cycle?
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Which behavior is exhibited by the ram during the mating process?
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What hormone primarily regulates the oestrous cycle in ewes?
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What occurs when the concentration of progesterone falls?
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What triggers ovulation of the mature follicle?
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Which hormone is likely to inhibit FSH release from the anterior pituitary?
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Which factors have been shown to influence ovarian function synergistically with gonadotrophins?
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What role does growth hormone (GH) play in ovarian function?
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Which statement about FSH is true?
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What is a characteristic effect of LH release in female reproductive physiology?
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What is the average age at which oestrus occurs in heifers?
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Which of the following factors is NOT mentioned as influencing the duration of oestrus?
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What is the average length of the oestrous cycle in cows?
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What phenomenon describes cows that do not show overt signs of oestrus but still have normal cyclic activity?
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How long does ovulation typically occur after the end of oestrus?
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Which breed of cows has been suggested to have a shorter average duration of oestrus?
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What common issue is attributed to delayed breeding in cattle?
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Which condition may delay the onset of puberty in young cattle?
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What is the average length of oestrus in domestic sows?
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Which period is primarily associated with oestrus in wild pigs?
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What effect does reduced day length have on the interval from weaning to oestrus?
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What type of activity suppresses cyclical activity in sows during lactation?
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How long does copulation generally last in domestic sows?
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What hormonal state is often observed in sows 2 days after farrowing?
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What is a definite behavioral sign of a sow approaching oestrus?
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What behavior indicates that a sow is in a state of oestrus during mating?
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Study Notes
Animal Breeding Patterns
- Animals typically breed once a year, with parturition occurring in spring, favoring progeny growth in warmer weather and abundant food supply for lactation.
- Domestication extends breeding seasons; domesticated cattle may breed year-round but tend to revert to natural cycles.
- Sexual receptivity, or being 'in heat', is required for breeding, characterized by oestrous cycles leading to ova release from the ovaries.
Puberty and Reproductive Maturity
- Young female animals do not exhibit cyclic sexual receptivity until puberty, which marks reproductive capability.
- Puberty occurs before physical maturity in females; efficiency in reproduction increases with age and maturation.
- No equivalent of menopause exists in domestic species, and cyclic activity may be interrupted by pregnancy, lactation, or pathological conditions.
Hormonal Regulation in Reproduction
- Pulsatile release of LH (Luteinizing Hormone) initiates cyclic activity; progesterone inhibits LH secretion during this cycle.
- Decreased progesterone from corpus luteum regression stimulates LH release, triggering ovulation through oestradiol increase.
- FSH (Follicle-Stimulating Hormone) plays a crucial role in initiating follicular growth, alongside LH for ovulation.
Age and Nutritional Influences on Puberty
- Age at first oestrus varies between 7 to 18 months, with nutrition and season of birth affecting timing.
- Poor feeding or calfhood diseases can delay puberty; some heifers may not ovulate during their first heat.
Oestrous Cycle Characteristics
- In heifers, average oestrous cycle length is around 20 days, while cows average 21 days, ranging between 18-24 days.
- The duration of oestrus historically averages about 15 hours, though modern breeds like Holstein and Jersey may have shorter durations of around 8 hours.
- The efficiency in detecting oestrus is crucial for artificial insemination, as oversight can delay breeding.
Signs of Oestrus and Mating Behaviour
- In ewes, signs of heat include restlessness, seeking rams, and physical interactions like pawing and nipping.
- Oestrous sows show signs like vulva swelling, restlessness, and distinctive vocalizations approaching heat, characterized by standing still during mating.
- Understanding the signs leading up to and during oestrus improves breeding success in both cattle and pigs.
Influence of External Factors
- Artificial manipulation of the photoperiod can advance the seasonal onset of sexual activity in domesticated animals.
- Stress can complicate hormonal readings; for instance, prolactin levels are hard to measure accurately due to stress interference.
Duration of Oestrus in Different Species
- Average oestrus duration in mature ewes is around 30 hours, while immature ewes may experience shorter oestrus.
- In sows, oestrus typically lasts about 53 hours with ovulation occurring between 38 and 42 hours after heat onset.
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Description
This quiz explores the breeding patterns of animals in nature, focusing on annual cycles and the optimal conditions for parturition. Learn about how factors such as light, warmth, and food availability influence reproductive timing, as well as the impact of domestication on breeding seasons.
